Patent GB-1182112-A (GB)
Title: Improvements in or relating to machining apparatus.
IPC: B24B49/04
Filed: 1966-05-03
Abstract: 1,182,112. Grinding. NEWALL ENG. CO. Ltd., and W. K. TEMPE. 27 April, 1967 [3 May, 1966], No. 19529/66. Heading B3D. [Also in Division G4] A caliper gauge for measuring a dimension of a workpiece which dimension changes during machining of the workpiece comprises:- (i) an anvil providing a first jaw, (ii) an arm which provides a second jaw and which is movable relative to the anvil to move the jaws towards and away from each other, (iii) means connected between the anvil and the arm for urging the two jaws together, (iv) a diffraction grating fixed with respect to the anvil, (v) a similar grating fixed with respect to the arm, (vi) a light source positioned such that movement of one jaw relative to the other causes the formation of optical interference fringes, and (vii) photo-electric transducing means for counting fringes produced during the movement thereby to provide a measure of the relative position of the two jaws. A gauge for cylindrical workpieces 28 includes a casing 10 at one end of which is secured a yoke 11 comprising members 12, 13, 14, 15. Along the member 15 is disposed a jaw piece 16 carrying a jaw insert 17. Anti-friction bearings 18, 19 mounted in the yoke 11 support a rod 20 carrying a jaw insert 21. Anti-friction bearings 22, 23 mounted in the yoke 11 support a rod 24 for movement at 45 degrees to the movement of the rod 20; the rod 24 carries a head 25 having a workpiece-contacting surface 26 parallel to a line connecting the jaw inserts 17, 21. The rods 20, 24 are interconnected by arms 29, 30, mounted on shafts 31, 32, having slots 33, 35 engaging pins 34, 36 on the rods 20, 24 and carrying meshing quadrant gears 44, 39. The shaft 31 is biased to close the gauge jaws by a clock spring 45 or by gravity bias with a geared connection to the shaft 31. The shaft 32 carries a knob 43 for manually altering the position of the rods 20, 24. The rod 24 carries a roller 38 running in a groove 37 in one half 42 of a cover, to prevent rotation of the rod 24. A plate 50 secured to the rod 20 has a longitudinal aperture 53 in which a diffraction grating 54 is held by bars 57, 58 attached to the plate 50 by screws 59, 60; helical springs 61 press the grating on to grub screws 62. A lamp 64 is enclosed in a casing 63 with a window 68. A diffraction grating 67 secured to an angle-plate 66 spans the window 68. Photo-cells 65 are disposed opposite slits 69 in a mask 69a, the output from a cell depending on the location of the bands of the fringe system produced by the two diffraction gratings which have their gratings lines at a slight angle to each other. The plate 50 carries a miniature bearing running in a groove in the casing 10 to prevent rotation of the rod 20. Signals produced by the gauge as the workpiece diameter reduces during grinding are fed to a digital counter 80, having manual resetting means 81, the values of the counter being sensed by comparators 82, 83, 84 which, at appropriate points in the cycle, send signals to a drive control 76 to set a selector switch 75 in positions F, S, R, in which an incremental drive 74 causes fast, slow and reverse feed of the grinding wheel 73.